Multi-component fibres

ABSTRACT

A multi-component fibre includes at least two elongated fibre bodies. A first fibre body consists of a first material including a phase change material and a second fibre body consists of a second material and encloses the first fibre body. The phase change material is non-encapsulated or in raw form and the first material includes a viscosity modifier selected from polyolefines having a density in the range of 890-970 kg/m 3  as measured at room temperature according to ISO 1183-2 and a melt flow rate in the range 0.1-60 g/10 minutes as measured at 190° C. with a 21.6 kg weight according to ISO 1133. Further, a textile, a fabric and an absorbent article include the multi-component fibre.

TECHNICAL FIELD

The present invention relates to multi-component fibres comprising phasechange material, textiles and fabrics (e.g. knitted, woven and nonwovenfabrics) comprising the multi-component fibres and absorbent articlescomprising the multi-component fibres.

BACKGROUND

The thermo-regulating system of a human being aims to maintain aconstant core temperature and skin temperatures within a range thatvaries between different body parts. Comfortable skin temperatures arewithin the range 28-33° C. Outside this temperature range, the bodyexperiences discomfort.

The body controls the rate of heat exchange with the environment byregulation of the skin blood flow. Sweat production (evaporative heatloss) or shivering (heat production) sets in at larger deviations inbody temperature.

The capacity and efficiency of the human thermo-regulating system israther limited. Putting on or taking off clothes helps the body to staywithin the comfortable temperature limits at different activity levelsand ambient conditions for longer periods of time. However, it is notalways appropriate or possible to put on or take off garments in aculturally acceptable way or it may be physically impossible ordifficult. This applies particularly to garments like underwear orabsorbent articles. Clothes and absorbent articles with built-inthermo-regulating properties would be able to maintain comfort withoutputting on or taking off clothes. Such clothing and absorbent articleswould reduce discomfort caused by accumulation of sweat/moisturetherein, and also shivering, which is rather unpleasant.

Integration of phase change materials (PCMs) in clothes is one way ofachieving thermo-regulating properties. When skin temperatures increase,the PCM melts and absorbs heat released from the skin. Then, when thetemperature drops, the PCM crystallizes and the stored heat is releasedagain. In this way, variations in skin temperature can be suppressed andthe temperature kept within the comfort zone. Not only products in theform of clothes and absorbent articles may benefit from incorporatingPCM but also textiles used for e.g. for bed linen, pillow covers,blankets, furniture, car seats and footwear.

Textiles incorporating PCM may also be used in domestic andinstitutional applications like carpets and curtains in order to evenout temperature fluctuations between day and night and thereby lower theenergy costs for heating (night time) and air conditioning (day time).

The most common method of incorporating PCMs into textiles is by coatingfabrics with a polymeric binder containing the PCM in microcapsules. Thethermo-regulating effect is dictated by the coating weight. Further, theamount of microcapsules that can be added in the coating is limited, sothe thermoregulating effect will be limited. In addition, applyingmicroencapsulated PCM as part of a coating has several drawbacks besidesthe problem above and the high cost of microcapsules. Properties likeair permeability and moisture permeability are impaired, which willaffect the thermal comfort in a negative way. Further, increasing theadd-on of coating results in a stiffer and less elastic fabric which isless comfortable to wear. Also surface properties like wetting may benegatively affected by the presence of a coating. This is especiallyimportant when dealing with training clothes or absorbent articles sincea desired property of such articles is the ability of transportingbodily fluids on fibre surfaces.

The drawbacks associated with coatings can be avoided if the PCMmicrocapsules are incorporated inside the fibres. An added benefit isthat the microcapsules are more durably bound to the fibres and canwithstand laundering. Incorporation of microcapsules is possible in wetspun acrylic fibres and wet spun cellulose fibres but the thermalefficiency is rather low (less than some 10 to 30 J/g) since the amountof PCM that can be incorporated is restricted by factors such asspinability and sufficient fibre strength.

The dominating synthetic fibre used today is polyester, which ismanufactured by means of melt spinning. Incorporation of microcapsulesin standard meltspun fibres has so far been restricted for severalreasons. The microcapsules must be able to withstand the hightemperatures and shear forces encountered in the melt spinning process.Other reasons are the size of the capsules (1-10 μm) and the fact thatparticulate filler will increase the melt viscosity tremendously makingmelt spinning of thin fibres very difficult.

When one makes fibres with a content of PCM, it is the intention toobtain as high a thermo-regulating effect as possible per unit charge ofPCM. In this perspective, the shell of the microcapsules is a ballastand an obstacle for energy transport. In order to achieve a fastexchange of energy between the skin of a human body and the PCMincorporated in a fibre, any unnecessary hindrance has to be minimized.Also, in order to load the fibrous material with as much PCM aspossible, any unnecessary material component should be minimized.

If PCMs are to be used in melt spun fibres without beingmicroencapsulated, that is, in a raw form, they have to be confinedwithin the fibre. A solution is to use multi-component fibres with acore/sheath structure or a so called island-in-the-sea structure so thatthe PCM is trapped inside the fibres. However, a number of difficultieshave to be overcome.

In “Effect of phase change material content on properties ofheat-storage and thermo-regulated fibres nonwoven”, Indian Journal ofFibre & Textile Research, Vol 28, September 2003, pp. 265-269, a methodof spinning fibres, comprising phase change material in raw form isdescribed. Core/sheath fibres were melt spun with n-eicosane (as PCM)and a blend of polyethylene and ethylene-propylene copolymer in thecore. The sheath was made from polypropylene. The maximum PCM contenttested was 21 wt-% and a latent heat of 32 J/g of fibres was reached.However, only some 50-60% of the theoretically possible latent heat wasrealised indicating that a significant portion of PCM in the fibre coredid not participate to the melting/crystallisation.

Further, WO 02/24992 A1 mentions that PCM in raw form is used whenspinning fibres. But the examples show the phase change materialenclosed in microcapsules and no examples with non-encapsulated phasechange material are disclosed.

WO 2006/086031 A1 mentions the use of modified forms ofethylene-propylene co-polymers and polar copolymers (e.g.ethylene-co-vinyl lacetate polymer) to facilitate the dispersion of thephase change material in the core material. Fibres having a high contentof phase change material and high values of latent heat are notdisclosed.

U.S. Pat. No. 7,160,612 B2 also mentions PCM in raw form can be usedwhen spinning fibres. The latent heat and the strength of the fibres arenot satisfactory.

US 2007/0089276 A1 describes melt spun multi-component fibresincorporating PCM in raw form. The latent heat is not disclosed.

U.S. Pat. No. 7,241,497 A1 discloses a multi-component fibre comprisingthermo-regulating material dispersed therein. The latent heat and thestrength of the fibres are not satisfactory.

Polymeric phase change materials have also been used for spinningfibres, but although such phase change material has a higher viscositythan low molecular hydrocarbon waxes and thereby may not need to bemixed with a viscosity modifier, they are not very efficient as theypossess quite low values of latent heat.

Thus, there is a need for fibres comprising high amounts of phase changematerial, where the fibres have a high latent heat combined with a goodmechanical strength. Such fibres have not yet been described.

There is thus a need to develop multi-component fibres comprising phasechange material with a good latent heat effect and having high strength.It is the aim of the present invention to solve the above problems.

SUMMARY

The present invention relates to a multi-component fibre, comprising atleast two elongated fibre bodies, wherein a first fibre body consists ofa first material comprising a phase change material and a second fibrebody consists of a second material and encloses the first fibre body.The phase change material is non-encapsulated or in raw form and thefirst material comprises a viscosity modifier selected from polyolefinshaving a density in the range of 890-970 kg/m³ as measured at roomtemperature according to ISO 1183-2 and a melt flow rate in the range0.1-60 g/10 minutes as measured at 190° C. with a 21.6 kg weightaccording to ISO 1133.

Further, the present invention relates to a textile material comprisingthe multi-component fibres.

A fabric comprising the multi-component fibres is also disclosedaccording to the present invention.

Further, the present invention concerns an absorbent article comprisingthe multi-component fibres.

SHORT DESCRIPTION OF THE FIGURES

FIG. 1 a)-d) illustrates different embodiments of multi-component fibresin cross-section according to the invention.

FIGS. 2 and 3 show further embodiments of multi-component fibres incross-section according to the invention.

FIG. 4 discloses a sanitary napkin according to an embodiment of thepresent invention.

FIG. 5 discloses a cross-section of the sanitary napkin in FIG. 4.

FIG. 6 shows a schematic illustration of a cross section of a downstreampart of a spinneret designed for core/sheath bi-component fibres.

FIG. 7 shows a schematic illustration of an exemplary process for makinga multi-component fibre according to the invention.

FIG. 8 shows a graph with the Magnitude of complex viscosity at 190° C.and 10 rad/s, versus wt-% RT 27 for different mixtures of polyethyleneand RT 27. RT 27 is a paraffin wax produced by Rubitherm GmbH, Berlin,Germany.

DEFINITIONS

The draw ratio (DR) is defined as the velocity ratio (V2/V1) in thesolid state drawing process, that is, DR=V2/V1. V1 is the filament speedafter the melt drawing process. V2 is the speed after the solid statedrawing process.

For a given material composition Titer is an indirect measure of thefilament diameter and is expressed in units of gram per 1000 or 10000meter of filament (Tex or dTex, respectively).

Tenacity is a measure of filament strength (maximum force sustained bythe filament during the tensile test divided by the filament titer) andis expressed in units of cN/Tex.

Modulus is a measure of filament stiffness and is calculated as theforce at 1% strain divided by the filament titer and is expressed inunits of cN/Tex.

Melt flow rate, MFR, is an inverse indicator of molecular weight of apolymer. That is, for a given polymer, the MFR will decrease withincreasing molecular weight.

By PCM efficiency is here meant the ratio obtained by dividing the heatof fusion of the first material comprising the PCM by the heat of fusionof the pure PCM and by the weight fraction of PCM in the first materialcomprising the PCM. The PCM efficiency is expressed in units of percentand is calculated using the formula:

PCM Efficiency=ΔH_(mix)/(w _(PCM) *ΔH _(PCM))*100

where ΔH_(mix) is the measured heat of fusion of the first materialcomprising the PCM (PCM+viscosity modifier) and w_(PCM) is the weightfraction of PCM and ΔH_(PCM) is the measured heat of fusion of the purePCM.

By thermal efficiency is here meant the ratio obtained by dividing theheat of fusion of the multi-component fibre by the heat of fusion offusion of the pure PCM and by the weight fraction of PCM in themulti-component fibre comprising the PCM. The thermal efficiency isexpressed in units of percent and is calculated using the formula:

Thermal Efficiency=ΔH/(w _(PCM) *ΔH _(PCM))*100

where ΔH_(fibre) is the measured heat of fusion of the multi-componentfibre comprising the PCM and w_(PCM) is the weight fraction of PCM andΔH_(PCM) is the measured heat of fusion of the pure PCM.

A textile is a flexible material comprised of a network of naturaland/or artificial fibers often referred to as threads or yarns. Yarn isproduced by spinning raw wool fibers, linen, cotton, or other materialon a spinning wheel to produce long strands known as yarn. Syntheticyarns are also available in the form of filament yarn. Textiles areformed by weaving, knitting, crocheting, knotting, or pressing fiberstogether. Textiles can be made from many materials. These materials comefrom four main sources: animal, plant, mineral, and synthetic.

A fabric is a textile material. The word fabric is commonly used intextile assembly trades (such as tailoring and dressmaking) as a synonymfor textile. However, there are subtle differences in these terms.Textile refers to any material made of interlacing fibres. Fabric refersto any material made through weaving, knitting, crocheting, or bonding.Generally, fabrics can be said to be fibre-based products having asubstantial surface extent in relation to their thickness. Nonwovens arealso included in the definition.

Nonwoven fabrics are those which are neither woven nor knit, for examplefelt. They are typically manufactured by putting staple fibers togetherin the form of a sheet or web, and then binding them either mechanically(as in the case of felt, by interlocking them with serrated needles sothat the inter-fiber friction results in a stronger fabric), with anadhesive, or thermally (by applying binder (in the form of powder,paste, or polymer melt) and melting the binder onto the web byincreasing temperature). Other manufacturing techniques involve thedirect thermal bonding of meltspun fibres. Spunlaid nonwovens are madein one continuous process. Fibers are spun and then directly dispersedinto a web by deflectors or can be directed with air streams. Severalvariants of this concept are available. Spunbond has been combined withmeltblown nonwovens, co-forming them into a layered product called SMS(spunbond-meltblown-spunbond). Meltblown nonwovens have extremely finefiber diameters but are not strong fabrics. Spunlaid is thermally bondedor bonded using a resin.

In the following, the expression “core material” will sometimes be usedinstead of “first material” and “sheath material” will sometimes be usedinstead of “second material”.

The expression “raw form” is intended to mean that the PCM is introducedin its raw form at the manufacturing of the multi-component fibre, i.e.that the PCM is not encapsulated, the PCM is neither carried on or byanother material solid at the spinneret temperature during spinning ofthe multi-component fibre, such as soaked into a porous structure,wherein the structure is solid at the spinneret temperature duringspinning of the multi-component fibre. Thus, the PCM is considered as in“raw form” in spite of it being mixed with the viscosity modifier atmanufacturing the multi-component fibre.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to multi-component fibres having atemperature regulating property by means of incorporating phase changematerial.

The multi-component fibres thus have the ability to absorb and releaseheat while maintaining a constant temperature. The multi-componentfibres can be used in various articles to provide thermal regulatingproperties. Articles, such as clothes or absorbent articles, worn closeto, or in contact with the skin of a user will give a comfortablefeeling to the user. If, for example, a piece of clothing or a top sheetin an absorbent article comprises the multi-component fibres accordingto the present invention, the clothing or article may even outvariations in the skin temperature so that it is kept within the comfortzone. Worn close to the body of a user, the multi-component fibers willhelp the user feel comfortable during varying physical activity, varyingambient conditions or when the skin temperature undergoes it's normaltemperature fluctuations due to for example emotional influence orduring circadien rythm. If a top sheet in an absorbent article comprisesthe multi-component fibres according to the present invention, thearticle may absorb heat from the user making the user perspire less.

This is especially advantageous if a dense article with low vaportransmission is used in contact with the user's body, in order to avoidmoisture against the skin of the user. Moisture on the skin of a user isa problem with regard to both absorbent articles and textile materials,which may lead to skin problems.

The present invention thus relates to a multi-component fibre 10, asshown in FIG. 1, comprising at least two elongated fibre bodies 11, 12,wherein a first fibre body 11 consists of a first material comprising aphase change material and a second fibre body 12 consists of a secondmaterial and encloses the first fibre body 11, wherein the phase changematerial is in raw form and the first material comprises a viscositymodifier selected from polyolefines having a density in the range of890-970 kg/m³ as measured at room temperature according to ISO 1183-2and a melt flow rate in the range 0.1-60 g/10 minutes measured at 190°C. with 21.6 kg weight according to ISO 1133.

The expression “raw form” is intended to mean that the PCM is introducedin its raw form at the manufacturing of the multi-component fibre, i.e.that the PCM is not encapsulated, the PCM is neither carried on or byanother material solid at the spinneret temperature during spinning ofthe multi-component fibre, such as soaked into a porous structure,wherein the structure is solid at the spinneret temperature duringspinning of the multi-component fibre. Thus, the PCM is considered as in“raw form” in spite of it being mixed with the viscosity modifier atmanufacturing the multi-component fibre.

It has been found that polymers having a melt flow rate in the range 0.1to 60 g/10 minutes measured at 190° C. with 21.6 kg weight are suitableas viscosity modifiers in the multi-component fibre. Many of theefficient PCM materials are low molecular compounds and such compoundspossess low viscosities at the relevant processing temperatures(180-300° C.). In order to make multi-component fibres with a sheathmaterial, the second material, having a higher viscosity at theprocessing temperature, the inventors have now found that if the phasechange material is mixed with a polyolefin having a melt flow rate inthe range 0.1-60 g/10 minutes, a fibre having high latent heat and whichis strong is obtained. The polyolefin is a viscosity modifier, whichincreases the viscosity of the first material of the multi-componentfibre.

It has been found that a low amount of a viscosity modifier having amelt flow rate in the range 0.1-60 g/10 minutes may be used, which is anadvantage for the thermal efficiency in terms of specific latent heatand at the same time allow the full utilisation of the inherent specificlatent heat of melting/crystallisation of the phase change material. Ifa higher value than 60 g/10 minutes is used, the viscosity will be toolow and the mixture will not be possible to process a fibre. The mixturewill be “watery”, i.e. very thin. A value lower than 0.1 g/10 minutes ofthe viscosity modifier might lead to curling of the fibres and fibrespinning may not be possible.

Other disadvantages with using low viscosity materials in melt spinning,such as back flow and leakage in screw extruders and gear pumps, arealso avoided when mixing the phase change material with a polyolefinhaving a melt flow rate in the range 0.1-60 g/10 minutes. Then the firstmaterial will have a viscosity high enough to process at the processtemperature.

Further, the viscosity modifier may have a density greater than 920kg/m³, preferably greater than 950 kg/m³ measured at room temperatureaccording to ISO 1183-2.

The phase change material is compatible with the viscosity modifier inthe melt, while it separates into a pure phase upon cooling. It isbeneficial to use a viscosity modifier with a high density. The effectof the modifier would be higher and a lower amount would be needed. Thisleads to a more efficient use of the inherent specific heat of fusionper gram of phase change material. A PCM efficiency as high as orgreater than 90% can be obtained, as disclosed in Example 2.

The viscosity modifier may have a melt flow rate in the range of 0.1-50g/10 minutes, preferably 0.1-20 g/minutes, more preferably 0.1-10 g/10minutes as measured at 190° C. with a 21.6 kg weight according to ISO1133. The lower the melt flow rate which is used for the viscositymodifier, the less amount of viscosity modifier is required to bring theviscosity of the first material comprising the phase change material upto a level adequate for the processing of the first material into amulti-component fibre. This is also shown in Example 1 below. Further,it is disclosed in Example 1 that an MFR lower than 10 g/10minutes wasenough to lower the concentration to less than about 30 wt-% of theviscosity modifier in the first material to increase the viscosity intothe range of standard polymer grades used for melt spinning of fibres.The first material can further comprise additives which are conventionalto use when producing fibres. Additional, a compatibilisator could beincluded in the first material in order to improve the boundary layerbetween the first and second fibre bodies.

The phase change material may have a latent heat of at least 100 J/g andpreferably at least 140 J/g. These values are good in order to obtainfibres having a latent heat which is efficient and which will give thethermo-regulating effects.

Further, the first material comprising the PCM may have a PCMefficiency, as measured by the ratio ΔH_(mix)/(w _(PCM)*ΔH_(PCM))*100,which is at least 90 expressed in %, preferably at least 95%. A high PCMefficiency means that the PCM is utilised in an efficient way. The highefficiency is obtained by for example the density of the viscositymodifier and the MFR of the viscosity modifier.

Further, the multicomponent fibre comprising the phase change materialmay have a thermal efficiency, as measured by the ratioΔH_(fibre)/(w_(PCM)*ΔH_(PcM))*100, which is at least 60 expressed in %,preferably at least 70, more preferred at least 75. A high thermalefficiency means that the PCM is utilised in an efficient way. The highefficiency is obtained by for example the density of the viscositymodifier, the MFR of the viscosity modifier and the choice of the secondmaterial.

Further, the viscosity modifier is present in less than 50% by weight,preferably less than 40% by weight and more preferably less than 30% byweight, calculated on the total weight of the first fibre body. When theamount of viscosity modifier can be kept low, a high latent heat can beobtained in the core. This may depend on the MFR value and the densityof the viscosity modifier.

The PCM may be present in more than 50% by weight, preferably more than60% by weight and more preferably more than 70% by weight, calculated onthe total weight of the first fibre body, in order to obtain a highlatent heat.

The first material comprises a phase change material and a viscositymodifier in the amount of at least 90% by weight together, calculated onthe total weight of the first material. The inventors have found that noextra elements in the first material are necessary in order to obtainthe fibres. This is possible since not encapsulated materials or noother carrying materials, such as porous structures, wherein the PCM isabsorbed, are not necessary.

According to the present invention, the phase change material isselected from hydrocarbon waxes with a melting point in the range 20-50°C., preferably in the range 25-45° C., and more preferably in the range27-40° C. These temperatures are suitable when consideringthermo-regulating material used for thermo-regulation of the environmentin proximity or in close contact of the human skin.

The phase change material is selected from linear hydrocarbon waxes.Preferred hydrocarbon waxes are n-Octadecane, n-Nonadecane, n-Eicosane,n-Heneiscosane or mixtures thereof. These waxes have melting pointswhich are suitable according to the present invention. These hydrocarbonwaxes have heats of fusions around 200 J/g in their pure form. However,for economical reasons it may be preferred to use less pure materials,having lower heats of fusion but being significantly cheaper.

The viscosity modifier may be polyethylene. The viscosity modifier issoluble in the phase change material at temperatures above the meltingpoint of the viscosity modifier, which polyethylene is. Further, verygood results have been obtained for multi-component fibres comprising apolyethylene viscosity modifier. The polyethylene may have a densitygreater than 950 kg/m³. This is good for the phase separation of thephase change material from the viscosity modifier as disclosed above.

The multi-component fibre has a latent heat of at least 20 J/g,preferably at least 30 J/g, and most preferred at least 40 J/g, asmeasured with a DSC-method in the range 0° C.-50° C.

The fibre will have strength greater than 10 cN/tex, preferably greaterthan 15 cN/tex and most preferably greater than 20 cN/tex. Thesestrengths are very good for multi-component fibres comprising phasechange material. Since a high latent heat can be obtained in the core,i.e. the first material, the core may constitute a less part of thefibre and the sheath can be thicker, which make the fibre stronger.Thus, the high efficiency of the latent heat of the PCM in themulti-component fibre and the low concentration of viscosity modifier inthe first material in order to achieve adequate melt processingaccording to the present invention makes it possible to obtain strongfibres.

According to the present invention there is also disclosed amulti-component fibre, wherein the ratio between the viscosity of thefirst material and the second material fulfils the condition0.1<Viscosity 1/Viscosity 2<10, where Viscosity 1 is the complexviscosity at the angular frequency of 10 rad/s of a first materialcomprising PCM and Viscosity 2 is the complex viscosity at the angularfrequency of 10 rad/s of the second material, wherein the viscositiesare measured at the extrusion temperature used during melt spinning,i.e. the set temperature of spinneret die.

With this relationship it is possible to produce multi-component fibresin a spinneret. Problems with co-extrusion, pressurizing and pumps withdevices such as screw extruders and gear pumps are avoided by thecondition above. Since the phase change material has a low viscosity,the viscosity modifier increases the viscosity of the first material,thus making it possible to reach the value defined above and therebymaking it possible to produce multi-component fibres. The choice of thePCM and viscosity modifier and the second material according to what isdisclosed in the present description will lead to the viscosityrelationship as disclosed.

The multi-component fibre may also comprise a second material which is afibre forming polymer that does not dissolve in the phase changematerial at temperatures above the melting point of the fibre formingpolymer or the softening point, in case of an amorphous polymer. Theefficiency of the PCM may then also be higher, since the PCM will beutilized in a higher degree if not disturbed by the presence of thesecond material dissolved in the phase change material. If the secondmaterial does not dissolve in the phase change material, the phasechange material does not dissolve in the second material. This willavoid problems related to migration of low molecular PCM. Such problemsmight be smell, loss of PCM (also during washing/laundry of objectscomprising the multi-component fibres) and sticky/greasy fibre surfaces.

For all multi-component fibres, produced in the examples, the thermalefficiency of the multi-component fibres was more than 70%, except wherethe second material was polypropylene. In the fibres wherein the secondmaterial was polypropylene, the efficiency was lower. However, suchfibres are very good compared to what has been possible to produce up tothis day of this kind. The lower efficiency might depend on that thepolypropylene could be dissolved in the phase change material. Thiscould also lead to some leakage of the phase change material. This couldbe a problem for fabrics used in for example clothing, which will bewashed and used for a longer time. However, when the fibres are used indisposable articles, this is not necessarily a problem.

For applications of the multi-component fibres of the invention inobjects that need regular laundering (e.g. garments and domestictextiles), it can be assumed that a continued migration of PCM out fromthe fibres will severely affect their thermal efficiency over time andlaundering cycles. For disposable objects (e.g. napkins) migration ofPCM might be a negligible problem.

The second material may comprise polymers selected from polyesters, suchas polyethylene terephthalate, polybutylene terephthalate,polytrimethylene terephthalate, polylactic acid; polyamides, such asPA-6,PA-66; PA-11 and PA-12; polycarbonate, polyoxymethylene,polyacrylates (e.g. PMMA), polyvinylidene difluoride or polypropylene.Apart from polypropylene, these polymers do not dissolve in the phasechange material, which is an advantage for the fibres. For example,migration and leakage of the phase change material is avoided. Any ofthe preferred second materials may be combined with any of the preferredphase change materials and viscosity modifiers.

The fibre may comprise at least one or more first fibre bodies and atleast one or more second fibre bodies. Any of the first materials andsecond materials can be used in the first or second fibre bodies. Thefirst materials may have different composition, which the secondmaterials also may have.

The present invention also relates to a textile material, comprising aplurality of multi-component fibres as disclosed in the presentdescription. The textile material may have latent heat of at least 10J/g and preferably of at least 20 J/g.

Further, the present invention relates to a fabric, comprisingmulti-component fibres as disclosed in the present description. Thefabric may have latent heat of at least 10 J/g and preferably of atleast 20 J/g.

Further, the present invention relates to an absorbent articlecomprising fibres as disclosed in the present description. The fibresused in the textile, fabric or the absorbent article may have any of theproperties as disclosed above.

Several embodiments of multi-component fibres are shown in FIGS. 1-3.The elongated fibre bodies may be arranged in different configurations.Core/sheath fibres are for example shown in

FIG. 1 a)-d), wherein the cross-section of the fibres is shown. Variousmulti-component fibres 10, 20, 30 and 40 are shown. A first fibre body,i.e. a core 11, 21, 31 and 41 is shown and is enclosed by a second fibrebody 12, 22, 32 and 42, i.e. a sheath is surrounding and enclosing thecore 11, 21, 31 and 41. However, further embodiments comprising morethan one first fibre body and/or more than one second fibre body is alsoencompassed by the present invention. In FIG. 1 is circular and trilobalcross-sectional shapes of the fibres disclosed. According to the presentinvention, a variety of other regular or irregular cross-sectionalshapes are also encompassed by the present invention. Such shapes couldbe for example oval, rectangular, square-shaped, multi-lobal,pentagonal, trapezoidal, triangular, wedge-shaped etc. Moreover, theshape of the first fibre bodies may also have the shapes as disclosedfor the fibres above.

The multi-component fibre 10 in FIG. 1 a) will now be described further,illustrating all embodiments of FIG. 1 which are similar to each other.The first fibre body 11 is arranged in the fibre and is enclosed by thesecond fibre body 12. The first fibre body 11 consists of a materialcomprising a phase change material. The first fibre body 11 forming thecore is concentrically positioned within the second fibre body forming12 the sheath. FIG. 1 b) illustrates a similar fibre, but the core 21 islarger compared to the core 11 in FIG. 1 a). The core 31 in FIG. 1 c) iseccentrically positioned within the second fibre body 32. The fibre 41in FIG. 1 d) is trilobal in shape.

In FIG. 2 is a multi-component fibre 50 disclosed wherein the firstfibre bodies 51 are arranged in an island-in-sea configuration. Thus,more than one first fibre body is disclosed in this embodiment. A secondfibre body 52 encloses the first fibre bodies 51 which form “islands” inthe second fibre body, i.e. the “sea”.

One or more additional fibre bodies enclosing the first fibre bodyconsisting of a material comprising a phase change material may also beinvolved in a multi-component fibre according to the present invention.The additional fibre bodies may consist of the same or differentmaterial.

The multi-component fibre in FIG. 3 is an example which comprises atleast a third fibre body additional to at least one first fibre body andat least one second fibre body. The fibre comprises first fibre bodies61 consisting of a first material and a second fibre body 62 consistingof a second material. Further, the fibre comprises third fibre bodies 63consisting of a third material. The third fibre bodies are also enclosedby the second fibre body 62. The third material may also comprise aphase change material and a viscosity modifier. Different phase changematerials and viscosity modifiers may be used in the first and thirdmaterial. The third material may be chosen according to the features asdefined above for the first material. However, the features are not thesame for the first and third material used in the same multi-componentfibre. All embodiments above may comprise the materials as defined abovefor the multi-component fibres.

If the multi-component fibres need to be stronger, additives such asnanoclays could be incorporated in the second material. The nanoclayworks as a reinforcing material. An additional benefit of incorporatingnanoclay in the second material is that the permeability to lowmolecular compounds can be reduced (tortuous path for diffusion). Thatis, lower migration of PCM through the second material.

Further, the present invention relates to an absorbent article, such asa diaper, a sanitary napkin, an incontinence article, a panty liner, bedprotector etc, comprising multi-component fibres according to above. Themulti-component fibres could be used in a nonwoven material, for exampleused as a top sheet in an absorbent article. This will give acomfortable feeling to the user.

The absorbent article may comprise a nonwoven material as a top sheet,wherein the nonwoven material comprises multi-component fibres accordingto the present invention, and further a bottom sheet and possiblyinterjacent layers as described below. An embodiment in the form of asanitary napkin 401 is illustrated in FIG. 4, wherein the sanitarynapkin comprises a nonwoven material comprising multi-component fibresaccording to the the invention as a top sheet 402. Also included is abottom sheet, which is not shown here, and possibly interjacent layersas described below.

The topsheet may consist entirely of the multi-component fibresaccording to the invention, the topsheet may also be a conventionaltopsheet manufactured from a wide range of materials such as woven andnonwoven materials (e.g. a nonwoven web of fibers). Suitable woven andnonwoven materials can be comprised of natural fibers (e.g. wood orcotton fibers), synthetic fibers (e.g. polymeric fibers such aspolyesters, polyamides, polypropylene or polyethylene fibers) or from acombination of natural and synthetic fibers, with the multi-componentfibers according to the invention mixed with the above-mentioned fibers.When the topsheet comprises a nonwoven web, the web may be manufacturedby a wide number of known techniques. For example, the web may bespun-bonded, carded, wet-laid, melt-blown, hydroentangled, combinationsof the above or the like.

The topsheet may comprise at least 50% by weight, preferably at least65% by weight and most preferably at least 70% by weight ofmulti-component fibers. At lower ratio multi-component fibers, saidfibers may be concentrated at the wearer-facing side of the topsheet, inorder to increase the thermo-regulating effect of said fibers.

FIG. 5 discloses a cross-section of the absorbent article in FIG. 4. Thebottom sheet 501 may consist of a flexible film, for example a plasticfilm. Examples of plastic materials in the film are polyethylene (PE),polypropylene (PP), polyester or some other suitable material, such as ahydrophobic nonwoven layer or a laminate of a thin film and a nonwovenmaterial. These types of material are often used in order to achieve asoft and textile-like surface on the bottom sheet 501. The bottom sheet501 can be breathable, so that it permits vapour to pass through whilealso preventing penetration by liquid. The breathable materials canconsist of porous polymer films, nonwoven laminates produced fromspunbonded and meltblown layers, and laminates produced from porouspolymer films and nonwoven materials.

The bottom sheet can have an adhesive attachment in the form of beads ofadhesive, for example, on the side of the bottom sheet that faces awayfrom the upper layer, to enable them to be secured in panties,underpants or knickers. A release material may be applied on top of theadhesive in order to protect the adhesive when the product is not inuse.

The absorbent product can also comprise an absorbent core 502 orstructure between the top sheet 503 and the bottom sheet 501. Theabsorbent core 502 can be constructed from one or more layers ofcellulose fibres, for example cellulose fluff pulp, airlaid, drydefibrililated or compressed pulp. Other materials that can be usedinclude, for example, absorbent nonwoven material, foam material,synthetic fibre material or peat. Apart from cellulose fibres or otherabsorbent materials, the absorbent core can also comprise superabsorbentmaterials, so-called SAP (superabsorbent polymers), which are materialsin the form of fibres, particles, granules, films or the like.Superabsorbent polymers are inorganic or organic materials that arecapable of swelling in water and are insoluble in water, which exhibitthe capacity to absorb at least 20 times their own weight of an aqueoussolution containing 0.9% by weight of sodium chloride. Organic materialsthat are suitable for use as a superabsorbent material can includenatural materials such as polysaccharides, polypeptides and the like, aswell as synthetic materials such as synthetic hydrogel polymers. Suchhydrogel polymers can include, for example, alkaline metal salts ofpolyacrylic acids, polyacrylamides, polyvinyl alcohol, polyacrylates,polyacrylamides, polyvinyl pyridines and the like. Other suitablepolymers include hydrolysed acrylonitrile-grafted starch, acrylicacid-grafted starch, and isobutylene maleic acid anhydride co-polymersand mixtures thereof. The hydrogel polymers are preferably readilycross-linked to ensure that the material remains essentially insolublein water. The preferred superabsorbent materials are also surfacecross-linked so that the external surface or the sheath of thesuperabsorbent particle, fibre, sphere, etc., has a higher cross-linkingdensity than the inner part of the superabsorbent. The proportion ofsuperabsorbents in an absorbent core can be between 10 and 90% byweight, or preferably between 30 and 70% by weight.

The absorbent core can comprise layers of different materials withdifferent characteristics with regard to their ability to receiveliquid, liquid distribution capacity and storage capacity. The absorbentcore is more often than not extended in the longitudinal direction andcan, for example, be rectangular, T-shaped or hourglass-shaped. Anhourglass-shaped core is wider in the front and rear parts than in thecrotch part, in order to provide effective absorption, at the same timeas the design makes it easier for the product to be formed close to andaround the wearer, thereby providing a better fit around the legs.

The absorbent product can also include a transport layer between the topsheet and the absorbent core. The transport layer is a porous, flexiblematerial and can comprise one or more of the following: airlaid,wadding, tissue, carded fibre web, superabsorbent particles orsuperabsorbent fibres. A transport layer has a high instantaneouscapacity to receive liquid and is able to store liquid temporarilybefore it is absorbed by the subjacent absorbent core. The transportlayer can cover the whole or parts of the absorbent core.

The top sheet, the bottom sheet and any interjacent materials are sealedat the edges of the product, which can be effected by thermal sealing,for example, or by some other conventional means.

The absorbent product can also comprise wings on its sides. It can alsocomprise elastic in order to provide better contact with the body whenthe product is being worn, and also to reduce leakage.

Components of the absorbent article which advantageously may comprise orentirely consist of the multi-component fibers according to theinvention are side-panels, belts and other components which are incontact with the wearers skin during use of the absorbent article.

A textile material comprising multi-component fibres according to aboveis also disclosed according to the present invention. The textilematerial is preferably used in clothing. The thermo regulatingmulti-component fibres are especially interesting to use in sportswear,work wear and underwear. In this type of applications themulti-component fibres of the invention can also be mixed with othertypes of fibres like synthetic fibres, cotton, wool and viscose. Thismay be an advantage regarding the good moisture transporting and/orabsorption properties of the latter type of fibres, contributing to thewear comfort. Clothing also includes health-care products, such asdrapes, gowns, face masks and hats, linings in jackets etc.

All features related to the multi-component fibres can also apply to thefibres in the fabric, in the absorbent article and in the textilematerial.

When phase change material is used in multi-component fibres, thestrength of the fibres may be lower compared to fibres not comprisingphase change material. For improving the strength of for example anonwoven material comprising the multi-component fibres according to thepresent invention, fibres having a higher strength could be mixed withthe multi-component fibres according to the present invention, whenproducing a nonwoven material.

The same would apply when the multi-component fibres are used in atextile material. When producing yarns for a textile material, some ofthe filaments used for the yarn production could be filaments, which arestronger than the filaments comprising the phase change material.

Further, the present invention relates to a method of producing amulti-component fibre 605, see FIG. 6, in which a section of a spinneretplate assembly is shown, comprising at least two elongated fibre bodies606, 607, wherein a first fibre body 606 consists of a first material602 and a second fibre body 607 consists of a second material 603 andencloses the first fibre body 606, wherein the method comprises:

-   -   a) to prepare a first material 602 by mixing a phase change        material with at least a viscosity modifier in molten form,    -   b) to cool the mixture into a solidified mixture,    -   c) to process the solidified mixture to be in a particulate        form,    -   d) to provide a second material 603,    -   e) to introduce the first 602 and second 603 materials to a        fibre extrusion spinneret plate assembly; and    -   f) to extrude the first 602 and second 603 materials so as to        form a multi-component fibre 605, wherein the second material        603 encloses the first material 602.

All steps are not shown in the Figure.

All the materials defined above may be used in the method of producingmulti-component fibres according to the present invention.

The present invention will now be described by the following examples.

Experimental Section

Methods

Density is measured according to ISO 1183-2.

Melt Flow Rate (MFR)

The ability of the polymer melts to flow through a capillary die underpressure was measured according to ISO 1133. MFR gives information aboutboth the molecular weight and the processability of the polymers, TheMelt Flow Rate (MFR) is defined as the weight of polymer in gramsflowing during 10 minutes through a capillary of specific diameter andlength by a pressure applied via prescribed alternative gravimetricweights for alternative prescribed temperatures. Measurements in thiswork were made at 190° C. using a weight of 21.6 kg, using a capillaryof diameter 2.095 mm and length 8.0 mm.

Rheological Evaluation

Rheological testing was performed by means of a Bohlin Controlled stresscone-and-plate rheometer (CS Melt) in oscillating mode (sinusoidal shearstrain amplitude was 1%). Plate diameter was 25 mm and Cone angle 5.4°.The sample chamber was purged with nitrogen during heating and testing.In this way curves showing the magnitude of the complex viscosity (inunits of Pascal seconds (Pas), vs. angular frequency, in units ofradians per second (rad/s)) were recorded.

DSC Analysis

Thermal properties were studied by means of a differential scanningcalorimeter, DSC 7 from

Perkin Elmer. In the first scan the sample was heated from 0° C. to 50°C. at 10° C./min. After annealing at this temperature for 1 minute thesample was cooled at 5° C./min. to 0° . The heating rate in the secondscan was 10° C./min. If not otherwise stated peak melting points andheat of fusion (calculated from the area under the melting peak and thesample weight) refers to the second scan from 0 to 50° C. The heat offusion, in units of Joule per gram (J/g), was calculated by means ofdividing the melting energy (area under the melting peak) with thesample weight.

Tenacity and Titer

Fibre properties (titer, tenacity and modulus) were evaluated by meansof a Vibrodyn (Lenzing) tensile tester. Gauge length was 20 mm andtesting speed was 20 mm/min. Samples were conditioned at 20° C. and 65%RH for at least 24 hours before testing. For a given materialcomposition Titer is an indirect measure of the filament diameter and isexpressed in units of gram per 1000 or 10000 meter of filament (Tex ordTex, respectively). Tenacity is a measure of filament strength (maximumforce sustained by the filament during the tensile test divided by thefilament titer) and is expressed in units of cN/Tex. Modulus is ameasure of filament stiffness and is calculated as the force at 1%strain divided by the filament titer and is expressed in units ofcN/Tex. Elongation is a measure of strain at break.

Preparation of Polymer-Wax Mixtures

Polymer pellets/powder was melted together with wax in a heated bakerunder slow agitation. The baker was heated to about 180° C. Duringheating the polymer particles gradually melt and the wax starts tomigrate into the particles which gradually swell in size. After sometime (5-30 minutes depending on polymer type, polymer particle size andbatch size) the swelled polymer particles coalesce into a viscous melt.The polymer-wax mixture was then cooled to room temperature. To furtherensure a homogenous mixture of wax and polymer the solid mixture was putin a heated Brabender kneader (180° C.) and was melt homogenized for 5minutes at 50 rpm. After melt homogenization in the Brabender kneaderthe material was left to cool where after the solid material was milledinto granules with a size of approximately 2-4 mm.

The first material can be produced and then stored before producing themulti-component fibre. Thus, all steps do not have to be performedimmediately after each other.

Melt Spinning of Bi-component Fibres

Melt spinning of fibres was done by means of an ESL lab spin machine,see FIG. 7. The spinneret 705 used had 24 exit holes with a diameter of0.6 mm. The spinneret 705 was configured for sheath/core bi-componentmelt spinning, see FIG. 6. The materials for the sheath and core aremelted separately by means of two 25 mm extruders 701 and 703, which inturn are feeding two gear pumps 702 and 704, FIG. 7. The two gear pumps702, 704 feed the spinneret 705. The extruder speed is automaticallyregulated by a control and feedback system ensuring a constant inletpressure to the gear pumps 702, 704. A section of the spinneret plateassembly is shown in FIG. 6. A first material 602 and a second material603 are loaded to the spinneret plate assembly forming a bicomponentfibre 605 having a core 606 and a sheath 607. A cross-section of thebi-component fibre 605 is also disclosed showing the core 606 and thesheath 607.

Hereby follows a more detailed description of the spin machine in FIG.7. The different elements in FIG. 7 are

701. Extruder for a first material comprising a phase change material

702. Gear pump for a first material comprising a phase change material

703. Extruder for a second material

704. Gear pump for a second material

705. Extrusion die (spinneret)

706. Take-off roller

707. Stretching roller pairs

708. Stretching roller pairs

709. Stretching roller pairs

710. Winder

The volumetric flow rate of sheath and core material is given by therespective gear pump speeds. The mass flow rate can be calculated fromthe volumetric flow rate and the density of the material at theprocessing temperature. The total (sheath+core material) volumetric flowrate was held constant at 24 cm³/minute in all experiments. By adjustingthe gear pump speeds for the sheath and core materials differentsheath/core ratios of the filaments can be achieved.

After leaving the spinneret die 705 the filaments 711 are first drawn(diameter reduction) in the melted state (melt drawing) duringsimultaneous cooling. The draw ratio in the melt drawing step betweenthe spinneret hole 712 and the take-off roller 706 is given by the ratioV1/V0, where V0 is the average melt speed in the spinneret holes 604(FIG. 6) (total volumetric output divided by the total hole area) and V1the linear speed of the take-off roller 6. In a second stage, in linewith the melt drawing, the solidified filaments are further drawnbetween several pairs of tempered stretching rollers 707, 708, 709. Thedraw ratio (DR) in the solid state drawing process is given by DR=V2/V1where V1 is the linear speed of the take-off roller 706 and V2 thelinear speed of the last pair of stretching rollers 709. The fibrestrength is significantly increased by the solid state drawing process.In practice there are a multitude of possible variations in the meltspinning process schematically illustrated in FIG. 7. For instance, thesolid-state drawing can be done in a separate step. For certainmaterials (e.g. PET) the solid state drawing step can be omitted if thedraw ratio V1/V0 is high enough corresponding to take-off speeds in therange of 5000-7000 meter per minute. In this case a satisfying strengthis developed by means of stress induced crystallization already in themelt drawing process.

Phase Change Materials

Examples of some hydrocarbon waxes that can be used as PCM arereproduced in table 1.

TABLE 1 Phase change properties of some common linear chain hydrocarbonsPhase Change Number of Melting point Heat of fusion Material carbonatoms (n) (° C.) (J/g) n-octadecane 18 28.2 242 n-nonadecane 19 32.1 187n-eicosane 20 36.6 246 n-heneicosane 21 40.2 200

Table 2 shows melting point and heat of fusion of some commercial PCMsavailable from Rubitherm Technologies GmbH, Berlin, Germany. Observethat the results are from the applicant's own measurements.

TABLE 2 Melting point and heat of fusion of some commercial hydrocarbonPCMs. Melting point Heat of fusion Grade [° C.] [J/g] RT 27 28 150 RT 3130 146 RT 35 34 150

EXAMPLES Example 1

Different amounts of a viscosity modifier in the form of polyethylenematerials (high density polyethtlene) were mixed with RT 27 (ahydrocarbon wax manufactured and supplied by Rubitherm GmbH in Germany,see Table 2). The melt flow rate of the polyethylene materials weredetermined by the method disclosed under “Melt Flow Rate”. The mixing ofthe viscosity modifier and the polyethylene was then made according tothe method disclosed under “Preparation of polymer-wax mixtures”. Thenthe viscosity of the different mixtures was investigated according tothe method “Rheological evaluation”. The angular frequency of 10 rad/sused for the comparison is chosen to roughly correspond to the wallshear rate in the cylindrical duct with a diameter of 2,5 mm as shown inFIG. 6.

The results are shown in FIG. 8 in a graph showing the Magnitude ofcomplex viscosity at 190° C. and 10 rad/s, versus wt-% RT 27. It isshown that the lower melt flow rate of the polyethylene the lower amountof polyethylene will be needed in order to obtain a high viscosity.Thus, a low melt flow rate of the viscosity modifier will increase theviscosity of the first material. For a given polymer, the lower the MFRof the polymeric viscosity modifier the less amount of viscositymodifier is needed to reach a given viscosity.

The shaded area in FIG. 8 gives an indication of shear viscosities oftypical polymer grades (e.g. polypropylene, polyamide, polyester)designed for melt spinning at their respective processing temperatures.Again, an angular frequency of 10 rad/s is taken as the reference.

In this specific example (hydrocarbon wax mixed with polyethylene asviscosity modifier), in order for the first material comprising PCM toreach a viscosity in the range of a second material together with whichit is to be co-extruded to produce the multi-component fibers of theinvention, it is seen that about 50 wt-% of polyethylene with MFR=120 isneeded to bring up the viscosity to an acceptable level (shaded area inFIG. 8). If the MFR is lowered to 8 only some 25-30 wt-% is needed. Byselecting an ultra high molecular weight polyethylene (UHMWPE) having aMFR <0.1 as viscosity modifier, only some 10-15 wt-% is needed.

However, it was experimentally found that extruding a mixture of RT 27with 10-15 wt-% UHMWPE through a capillary at a shear rate of 10 s-1produced severe melt fracture, a phenomena well known to those skilledin the art of polymer extrusion. This was confirmed by bi-componentfiber spinning (core/sheath configuration) using a first materialcomprising PCM (RT 27 mixed with 10-15 wt-% UHMWPE) and a melt spinninggrade of PP (HG 245 FB produced by Borealis) as the second material. Themolten filaments exiting the spinneret holes severely curled and fiberspinning was not possible. This type of melt fracture is sometimesdesignated “elastic turbulence” and is presumably caused by the veryhigh elasticity imparted by the very long molecular chains of the HMWPEpolymer. There is thus a lower limit on the MFR of the polymer that canbe used as viscosity modifier.

Example 2

The PCM efficiency of a polymer comprising PCM with regard to its amountof latent heat (heat of fusion/crystallization) is disclosed in Table 3.The polymer comprising PCM shall correspond to the first material in amulti-component fibre. The hydrocarbon wax RT 31 was mixed withdifferent polyolefins and was made according to the method disclosedunder “Preparation of polymer-wax mixtures” and the heat of fusion inthe range 0-50° C. was measured by means of DSC according to the DSCanalysis disclosed above.

TABLE 3 wt-% Heat of PCM wax fusion Efficiency Material (RT 31)^(d) J/g% FS1560 (HDPE)^(a) 65 93.7 99.4 MFR^(e) = 9^(e) 70 100.5 99.0 Density =956 kg/m³ 75 108.7 100.0 80 120.4 103.8 BL0521 (HDPE)^(a) 65 88.7 94.1MFR^(e) = 2.5^(e) 70 94.8 93.4 Density = 952 kg/m³ 75 102.3 94.1 80112.8 97.3 FL1500 (HDPE)^(a) 65 — — MFR^(e) = 8^(e) 70 — — Density = 950kg/m³ 75 — — 80 105.5 91.0 EZP2207 (LLDPE/butene)^(b) 65 — — MFR^(e) >65^(e,h) 70 85.7 84.4 MFR^(f) = 0.7^(f) 75 — — Density = 922 kg/m³ 80102.9 88.7 Elvaloy 3117 AC (Ethylene- 65 — — co-butyl acrylate, EBA)^(c)70 85.9 84.6 MFR^(e) > 80^(e,h) 75 — — MFR^(f) = 1.5^(f) 80 98.2 84.6Density = 924 kg/m³ HE445FB (PP)^(a) 65 — — MFR^(e) > 80^(e,h) 70 84.282.9 MFR^(g) = 11^(g) 75 — — Density = 903-910 kg/m³ 80 99.9 86.1RT31^(d) 100  145 100 ^(a)Available/supplied by Borealis^(b)Available/supplied by Equate ^(c)Available/supplied by DuPont^(d)Available/supplied by Rubitherm ^(e)g/10 minutes as measured at 190°C. with a 21.6 kg weight according to ISO 1133 ^(f)g/10 minutes asmeasured at 190° C. with a 2.16 kg weight according to ISO 1133 ^(g)g/10minutes as measured at 230° C. with a 2.16 kg weight according to ISO1133 ^(h)not measured by applicant, estimated level —no experiment made

High PCM efficiencies were obtained. Within the polyethylene family thematerial (FS1560) with the highest density showed the highest efficiencyregarding heat of fusion. As may be noted, one of the sample (20%FS1560) exceeds 100% PCM efficiency. This is probably due to smallvariations in the core/sheath ratio during the spinning process.

Example 3

In the following examples, the core material corresponds to the firstmaterial and the sheath material corresponds to the second materialaccording to the present invention.

In this Example a set of bi-component fibres with a sheath/corestructure were manufactured as described previously under “Melt spinningof bi-component fibres”. The core material was a mixture of 70 wt-% RT27and 30 wt-% HDPE (FL1500 manufactured by Borealis). The sheath was PP(HG 245 FB manufactured by Borealis). The melt spinning parameters arereproduced in Table 4.

TABLE 4 Gear pump speed, rpm (CORE) 3-6 Gear pump speed, rpm (SHEATH)7-4 Total flow rate, cm³/min 24 Take-off roller, m/min 250 Bottomroller, m/min/Temperature, ° C. 275/80  Middle roller,m/min/Temperature, ° C. 625/90  Top roller, m/min 750 Draw ratio (V2/V1)3.0 Extruder Temperatures, ° C. (core/sheath) 170, 180, 190/190, 200,210 Gear pump temperature, ° C. (core/sheath) 210/210 Spineretttemperature, ° C. 210

Some fibre properties are listed in Table 5.

TABLE 5 Core/Sheath Heat of Thermal ratio (based on Wt-% fusionefficiency Titer Modulus Tenacity Elongation weight) PCM [J/g] [%][dTex] [cN/Tex] [cN/Tex] [%]   0/100* 0 — — 11.0 270 29 196 30/70 2111.6 37 10.5 141 16 126 40/60 28 16.2 39 10.2 130 11 73 50/50 35 33.3 6310.7 126 8.4 47 60/40 42 43.8 70 9.5 142 7.6 34 *Monofilament.

The properties are obtained by the methods disclosed above in thebeginning of the experimental section.

The Thermal efficiency of the multi-component fibers is expressed as theratio ΔH_(fiber)/(w_(PCM)*AH_(PCM))*100. As can be seen from Table 5 thethermal efficiency increases from 37 to 70% by increasing theCore/Sheath ratio from 30/70 to 60/40 corresponding to an increase inPCM content from 21 to 42 wt-% based on the total fiber weight. Thermalefficiencies lower than 60% are considered to be low which means that asubstantial part of the added PCM does not take part in the meltingprocess.

It is likely that the low thermal efficiency is due to migration ofhydrocarbon wax from the core into the sheath where it is dissolved inthe amorphous parts of the polypropylene. This is also due to the factthat polypropylene is soluble in the hydrocarbon wax. If so, thermalefficiency will be partly lost since PCM dissolved in amorphous parts ofa polyolefin will have a low tendency to crystallize. For applicationsof the multi-component fibres of the invention in objects that needregularly laundering (e.g. garments and domestic textiles) it can beassumed that a continued migration of PCM out from the fibres willseverely affect their thermal efficiency over time and launderingcycles. For disposable objects (e.g. napkins) migration of PCM might bea negligible problem.

Example 4

In the following Example a set of bi-component fibres with a sheath/corestructure were manufactured as described previously under “Melt spinningof bi-component fibres”. The core material was a mixture of 35 wt-%RT31, 35 wt-% RT35 and 30 wt-% HDPE (FL1500 manufactured by Borealis).The sheath was PET (GL-BA 6105 with an intrinsic viscosity of 0.61measured according to ASTM D4603), supplied by TWD Polymere, Germany).The melt spinning parameters are reproduced in Table 6.

TABLE 6 Gear pump speed, rpm (CORE) 4-6 Gear pump speed, rpm (SHEATH)6-4 Total flow rate, cm³/min 24 Take-off roller, m/min 250 Bottomroller, m/min/Temperature, ° C. 275/80  Middle roller,m/min/Temperature, ° C. 625/80  Top roller, m/min 750 Draw ratio (V2/V1)3.0 Extruder Temperatures, ° C. (core/sheath) 170, 200, 210/280, 300,290 Gear pump temperature, ° C. (core/sheath) 230/280 Spineretttemperature, ° C. 280

Fiber properties are listed in Table 7.

TABLE 7 Core/Sheath Heat of Thermal ratio (based on Wt-% fusionefficiency Titer Modulus Tenacity Elongation weight) PCM [J/g] [%](dTex) (cN/Tex) (cN/Tex) (%) 30/70 21 23.8 78 10.3 388 21 80.5 40/60 2831.8 78 14.8 244 15.9 138.4 50/50 35 45.9 90 12.8 226 13.6 165.2

The thermal efficiency of the fibers with polyethylene terephthalate(PET) in the sheath (78-90%) is significantly higher than for the fiberswith PP in the sheath (37-70%), see example 3 above. This might beexplained by the fact that non-polar hydrocarbon waxes are not solublein the more polar PET and vice versa. For applications of themulti-component fibers of the invention, in which preventing loss of PCMthrough the sheath by migration/diffusion is important, it is thuspreferable that the second material forming the elongated fibre bodyenclosing the fibre body comprising the phase change material is a fibreforming polymer that does not dissolve in the phase change material attemperatures above the melting point of the fiber forming polymer (orsoftening point in case of an amorphous polymer). The strength of thefibres is very good for bi-component fibres comprising phase changematerial in the amounts according to above.

Example 5

In this Example a set of bi-component fibres with a sheath/corestructure were manufactured as described previously under “Melt spinningof bi-component fibres”. The core material was a mixture of 35 wt-%RT31, 35 wt-% RT35 and 30 wt-% HDPE (FL1500 manufactured by

Borealis). The sheath was PET (GL-BA 6105 with an intrinsic viscosity of0.61 measured according to ASTM D4603), supplied by TWD Polymere,Germany). The melt spinning parameters are reproduced in Table 8.

TABLE 8 Gear pump speed, rpm (CORE) 5 Gear pump speed, rpm (SHEATH) 5Total flow rate, cm³/min 24 Take-off roller, m/min 150, 300 Bottomroller, m/min/Temperature, ° C. 175, 325/80 Middle roller,m/min/Temperature, ° C. 600, 1200/80  Top roller, m/min 750, 1500 Drawratio (V2/V1) 5 Extruder Temperatures, ° C. (core/sheath) 170, 200,210/280, 300, 290 Gear pump temperature, ° C. (core/sheath) 230/280Spinerett temperature, ° C. 280

Fibre properties are listed in Table 9.

TABLE 9 Core/Sheath Heat of Thermal ratio (based on Wt-% fusionefficiency Titer Modulus Tenacity Elongation weight) PCM [J/g] [%](dTex) (cN/Tex) (cN/Tex) (%) 40/60 28 33.2 82 11.7 578 26.8 38.7 40/6028 32.4 80 7.1 570 26.2 28.2

The strength of the multi-component fibres of the invention can furtherbe increased by increasing the draw ratio during melt spinning as shownin this example where two set of fibres are produced with DR=5 anddifferent titer. Materials are the same as in example 4, in which DR was3 and the tenacity was higher in Example 5 for the core/sheath ratio40/60 compared to in Example 4 with the same core/sheath ratio 40/60.Fibres with maintained thermal properties are produced withsignificantly higher stiffness (modulus) and strength (tenacity) whenthe draw ratio is increased.

Example 6

Polyamide is used as the second material in this example. A set ofbi-component fibres with a sheath/core structure were manufactured asdescribed under “Melt spinning of bi-component fibres”. The corematerial was a mixture of 75 wt-% pure n-Eicosane (supplied by RoperThermals, USA) and 25 wt-% HDPE (FS 1560 manufactured by Borealis). Thesheath material was a fiber spinning grade of PA6 (Ultramid BS 703)supplied by BASF, Germany. The measured heat of fusion of the puren-Eicosane was 240 J/g. The melt spinning parameters are reproduced inTable 10.

TABLE 10 Gear pump speed, rpm (CORE) 4-5 Gear pump speed, rpm (SHEATH)6-5 Total flow rate, cm³/min 24 Take-off roller, m/min 250 Bottomroller, m/min/Temperature, ° C. 275/60  Middle roller,m/min/Temperature, ° C. 625/65  Top roller, m/min 750 Draw ratio (V2/V1)3.0 Extruder Temperatures, ° C. (core/sheath) 140, 170, 190/240, 270,280 Gear pump temperature, ° C. (core/sheath) 240/270 Spineretttemperature, ° C. 270

Fiber properties are reproduced in Table 11.

TABLE 11 Core/Sheath Heat of Thermal ratio (based on Wt-% fusionefficiency Titer Modulus Tenacity Elongation weight) PCM [J/g] [%](dTex) (cN/Tex) (cN/Tex) (%) 34/66 25.5 48 79 13 160 33 37 43/57 33 6582 11.8 165 27 44

Also in this example the thermal efficiency is high. This is probablydue to that fact that the more polar PA6 is not soluble in non-polarhydrocarbon waxes. For the sake of clarity, the non-polar hydrocarbonwaxes are neither soluble in the more polar PA6. The strength of thefibers is good already at a draw ratio of 3. By using a PCM with a highheat of fusion (240 J/g in this example), a HDPE with a high density(956) and low MFR (9), (allowing for a high PCM efficiency and lowconcentration of HDPE (still facilitating good processabilty)) as apolymeric viscosity modifier, and a sheath material with low solubilityof hydrocarbon wax PCM, strong multi-component fibers (27-33 cN/tex)with a high heat of fusion (48-65 J/g) can be manufactured already atmodest loadings of PCM of 25-33wt-%, based on total fiber weight.

For all multi-component fibres, except where the second material waspolypropylene, the thermal efficiency of the multi-component fibres wasmore than 70%. This might depend on that the polypropylene could bedissolved in the phase change material. Then, the phase change materialis not utilised in the same degree. This could also lead to some leakageof the phase change material. This could be a problem for fabrics usedin for example clothing, which will be washed and used for a longertime. However, when the fibres are used in disposable articles, this isnot necessarily a problem.

It is shown in the Examples that multi-component fibres according to thepresent invention have good latent heat, good PCM efficiency, goodthermal efficiency, high strength and are easy to produce.

1. A multi-component fibre comprising at least two elongated fibrebodies, wherein a first fibre body consists of a first materialcomprising a phase change material (PCM) and a second fibre bodyconsists of a second material and encloses the first fibre body, whereinthe phase change material is in raw form and the first materialcomprises a viscosity modifier selected from polyolefines having adensity in the range of 890-970 kg/m³ as measured at room temperatureaccording to ISO 1183-2 and a melt flow rate in the range 0.1-60 g/10minutes as measured at 190° C. with a 21.6 kg weight according to ISO1133.
 2. The multi-component fibre according to claim 1, wherein theviscosity modifier has a density greater than 920 kg/m³ as measured atroom temperature according to ISO 1183-2.
 3. The multi-component fibreaccording to claim 1, wherein the viscosity modifier has a melt flowrate in the range of 0.1-50 g/10 minutes as measured at 190° C. with a21.6 kg weight according to ISO
 1133. 4. The multi-component fibreaccording to claim 1, wherein the phase change material has a latentheat of at least 100 J/g.
 5. The multi-component fibre according toclaim 1, wherein the multi-component fibre comprises a first materialhaving a PCM efficiency, as measured by the ratioΔH_(mix)/(w_(PCM)*ΔH_(PCM))*100, of at least 90%.
 6. The multi-componentfibre according to claim 1, wherein the multi-component fibre has athermal efficiency, as measured by the ratioΔH_(fibre)/(w_(PCM)*ΔH_(PCM))*100, which is at least 60 expressed in %.7. The multi-component fibre according to claim 1, wherein the viscositymodifier is present in less than 50% by weight, calculated on the totalweight of the first fibre body.
 8. The multi-component fibre accordingto claim 1, wherein the PCM is present in more than 50% by weight, morethan 70% by weight, calculated on the total weight of the first fibrebody.
 9. The multi-component fibre according to claim 1, wherein thefirst material comprises the phase change material and the viscositymodifier in the amount of at least 90% by weight together, calculated onthe total weight of the first material.
 10. The multi-component fibreaccording to claim 1, wherein the phase change material is selected fromhydrocarbon waxes with a melting point in the range 20-50° C.
 11. Themulti-component fibre according to claim 1, wherein the phase changematerial is selected from linear hydrocarbon waxes.
 12. Themulti-component fibre according to claim 1, wherein the viscositymodifier is polyethylene.
 13. The multi-component fibre according toclaim 11, wherein the viscosity modifier is polyethylene with a densitygreater than 950 kg/m³.
 14. The multi-component fibre according to claim1, wherein the fibre has a latent heat of at least 20 J/g, as measuredwith a DSC-method in the range 0° C.-50° C.
 15. The multi-componentfibre according to claim 1, wherein the fibre has strength greater than10 cN/tex.
 16. The multi-component fibre according to claim 1, whereinthe ratio between the viscosity of the first material and the secondmaterial fulfils the condition 0.1<Viscosity 1/Viscosity 2<10, whereViscosity 1 is the complex viscosity at the angular frequency of 10rad/s of the first material comprising PCM and Viscosity 2 is thecomplex viscosity at the angular frequency of 10 rad/s of the secondmaterial, wherein the viscosities are measured at the extrusiontemperature used during melt spinning, i.e. the set temperature ofspinneret die.
 17. The multi-component fibre according to claim 1,wherein the second material is a fibre forming polymer that does notdissolve in the phase change material at temperatures above the meltingpoint of the fiber forming polymer or the softening point, in case of anamorphous polymer.
 18. The multi-component fibre according to claim 1,wherein the second material comprises polymers selected from polyestersand polyamides.
 19. The multi-component fibre according to claim 1,wherein the fibre comprises at least one or more first fibre bodies andat least one or more second fibre bodies.
 20. The multi-component fibreaccording to claim 1, wherein the fibre comprises at least one or morefirst fibre bodies, at least one or more second fibre bodies and atleast one or more third fibre bodies which consists of a third material.21. A textile material comprising the multi-component fibre according toclaim
 1. 22. A fabric comprising the multi-component fibre according toclaim
 1. 23. The fabric according to claim 22, wherein the fabric has alatent heat of at least 10 J/g.
 24. An absorbent article comprising themulti-component fibre according to claim 1.